(Article) Wrong concrete used in Kilkenny M9 bridge

IIMII

Irish Times, Wed, Oct 21, 2009

A SECTION of the N9/M9 which will link Waterford to Dublin by motorway will have to be dismantled after the wrong batch of concrete was used in its construction.
A section of the deck in the new bridge over the river Nore in Co Kilkenny will have to be dismantled after an on-site error, according to Kilkenny County Council engineer Joe Gannon.
He said approximately one sixth of the deck of the bridge was constructed with the wrong mix of concrete due to a computer error.
“They are telling us that it was a computer error. One batch of concrete that was supposed to go to one end of the site went here, and vice versa. As the client we don’t care what went wrong; we just want it sorted out.”
Mr Gannon said the concrete in the bridge was supposed to have a strength of 40 neutrons, but the concrete that was used had been intended for the central barrier.
“The concrete they put in, I think, has a design strength of 20 . I think it’s the concrete that would be used for a central barrier, I am told.”
A spokesperson for Sisk Road Bridge (SRB) said they were in talks with the cement contractor.
“SRB and its concrete supplier have been in discussion with Kilkenny County Council with regards to the remedial works at the Nore river bridge.
“There are no health and safety or environmental issues arising. There will be no cost to the local authority as a result of the works, which will take place in the short to medium-term, and will not affect the delivery of the project.”
A spokesman for the National Roads Authority (NRA) said quality control and identifying mistakes were all part of large building projects.
“Being able to identify the cause and effect is all part of quality control, and who is going to be responsible for payment is being dealt with through the contractors.”
© 2009 The Irish Times

http://www.irishtimes.com/newspaper/ireland/2009/1021/1224257144951.html

The Word Is Bor

You would think that the Irish Times would check their quotes unless of course the county engineer got it arseways. 40 neutron concrete? It's Newton. The compressive strength of the central barrier would be in the order of 28-35N. as well.

csd

40 neutrons, eh? Someone should tell the SI folk that the Newton has been replaced in Ireland!

/csd

Amtmann

Bad reportage alright. I presume this is the Carlow to Knocktopher scheme? Is the bridge in question part of any section we were hoping to open by the end of this year?

Bards

Furet wrote: »

Bad reportage alright. I presume this is the Carlow to Knocktopher scheme? Is the bridge in question part of any section we were hoping to open by the end of this year?

Don't think so, AFAIK the bridge in question is on the kilkenny to Carlow stretch of the M9

Roryhy

Furet wrote: »

Bad reportage alright. I presume this is the Carlow to Knocktopher scheme? Is the bridge in question part of any section we were hoping to open by the end of this year?

On the Carlow - Knocktopher section, due to open mid 2010.

Picture from Thompsons Engineering site-

Tech3

Roryhy wrote: »

On the Carlow - Knocktopher section, due to open mid 2010.

Picture from Thompsons Engineering site-

Big mistake and the bridge is fairly big to dismantle and put back up again. How long a delay are we looking at here? 2-3 months at least surely?

Roryhy

I don't think its that big a job really, i'd reckon its just one deck that needs to be removed. It was only one load of concrete and that doesn't go that far in a big structure like this. I don't think the completion date will move, extra man-hours will be needed but lets not get our knickers in a twist here.

dmeehan

does anyone really believe that it was a "computer error"?

Roryhy

dmeehan wrote: »

does anyone really believe that it was a "computer error"?

Well as we all know, theres no such thing as computer error, they do what they're told. Someone messed up, these things happen. At least they spotted it and it won't end in catastrophe months or years down the line when the concrete fails.

kaizersoze

Roryhy wrote: »

It was only one load of concrete and that doesn't go that far in a big structure like this.

They say it was 1 batch. Does 1 load = 1 batch?
Could a batch not contain several loads?

Roryhy

kaizersoze wrote: »

They say it was 1 batch. Does 1 load = 1 batch?
Could a batch not contain several loads?

Its possible Kaiser, oversight on my part, not familiar with the lingo.

canine

Its not a computer error if it was meant for somewhere else on the site ,it was a site error .I can see how this could happen alright you,re relying on someone on site to direct the truck driver to where he needs to go ,they had 2 pours on at the same time and got them mixed up .Im sure someone took the fall for this on site ,probably some junior engineer whose job it was to check the dockets .25 newton concrete will probly reach a strength of 40 newtons after 28 days but they wrer looking for 40 newtons initially which would reach 50 after 28 days

kaizersoze

Roryhy wrote: »

not familiar with the lingo.

Not overly familiar with it myself. That's why I asked.:)

marmurr1916

tech2 wrote: »

Big mistake and the bridge is fairly big to dismantle and put back up again. How long a delay are we looking at here? 2-3 months at least surely?

Probably less. The report says that only one section of the bridge needs to be replaced, not the entire bridge.

wellbutty

kaizersoze wrote: »

They say it was 1 batch. Does 1 load = 1 batch?
Could a batch not contain several loads?

A "batch" is a production run of concrete to a certain specification so yeah, one batch would almost certainly have multiple loads.

Roryhy wrote: »

I don't think its that big a job really, i'd reckon its just one deck that needs to be removed. It was only one load of concrete and that doesn't go that far in a big structure like this. I don't think the completion date will move, extra man-hours will be needed but lets not get our knickers in a twist here.

This won't effect the completion date. In acknowledging the error, Roadbridge have won themselves a few new friends as a lot of people weren't aware that concrete can have different strengths and how if unchecked, it can impact the safety of the structure!

canine wrote: »

Its not a computer error if it was meant for somewhere else on the site ,it was a site error .I can see how this could happen alright you,re relying on someone on site to direct the truck driver to where he needs to go ,they had 2 pours on at the same time and got them mixed up .Im sure someone took the fall for this on site ,probably some junior engineer whose job it was to check the dockets .25 newton concrete will probly reach a strength of 40 newtons after 28 days but they wrer looking for 40 newtons initially which would reach 50 after 28 days

The concrete would have been checked on arrival on the site using what's known as the "slump test". This is fairly crude in that you put the fresh concrete into a cylinder of a known height, then remove the cylinder and see how much the concrete has slumped!

As Canine said, this is the initial strength. Obviously it hardens to a design strength, this is almost achieved after 28 days and is measured using a "cube test" which is really a crush test.

In measurement terms, "40 Newton concrete" is effectively 40 apples on every square millimeter of area. Hope this helps

REFLINE1

canine wrote: »

Its not a computer error if it was meant for somewhere else on the site ,it was a site error .I can see how this could happen alright you,re relying on someone on site to direct the truck driver to where he needs to go ,they had 2 pours on at the same time and got them mixed up .Im sure someone took the fall for this on site ,probably some junior engineer whose job it was to check the dockets .25 newton concrete will probly reach a strength of 40 newtons after 28 days but they wrer looking for 40 newtons initially which would reach 50 after 28 days

It wasnt a site error-it was a balls up at the concrete batching plant.Two concrete wagons destined for the same site but with different grades of concrete on board,driver was given the wrong docket (or concrete batcher inputted the wrong truck reg in the manual entry part of the computer that spits out your delivery docket).Can happen very easily!
On a big site like that its impossible for the site team to know this as the docket would have read 40N concrete (C32/40)
As regards slump tests etc---nothing to do with strength of concrete-this is a quick test of the workability of the mix,nothing else.

Pretty expensive mistake for the concrete supplier--prob only spotted 28days after it happened when cube results came back!